This invention relates to a process and an apparatus for deodorizing malodorous substances.
Waste streams from sewage plants, rendering plants, barns and hog pens, as well as dung manure spreads and garbage-filled landfills, contain solids, liquids and/or gases from which foul odors may evolve. Such odors are objectionable to workers and inhabitants of the area, and in some cases, the odors are so objectionable as to cause partial or total shutdown of the facility.
Various schemes have been proposed for alleviating malodorous substances including aeration, incineration, scrubbing and/or deodorizing reactions.
Numerous methods involve the use of oxidizing agents. Waste or exhaust gas is deodorized by washing at least twice with active chlorine which is practically free from chlorine dioxide, followed by an alkaline washing (U.S. Pat. No. 3,923,955 issued Dec. 2, 1975 to Fattinger). Solid waste facilities are scrubbed for odor control with oxidizing agents such as sodium hypochlorite, chlorine, chlorine dioxide, or potassium permanganate (A. Serper, "Odor Control Systems for Solid Waste Facilities: Review and Selection", Solid Wastes Management Refuse Removal Journal 21, 5, pp. 22-24, 28, 31 (1978)--Pollution Abs. 054933-78-04121). Sewage farms and dung manure spreadings are sprayed with a composition comprising a stabilized aqueous solution of chlorine dioxide, isopropanol, didecyldimethyl ammonium chloride, a non-ionic surfactant, aromatic materials, stabilizing co-emulsifiers, and water (FR 2,696,643 A1 issued Apr. 15, 1994 to Rocchia--Derwent Abs. No. 94-146367/18). Waste gases from a sewage lift station are scrubbed with a hypochlorite solution produced electrolytically from a brine solution" (Tollefsrud, "Hypochlorite Kills Lift Station Odor", Water Sewage Works 126 1, p. 78 (1979)--C. A. 90 (16) 1127051f). Gases containing odiferous acidic contaminants are mist scrubbed with an aqueous reagent containing a mixture of an oxidizing agent and a base. Chlorine dioxide, hydrogen peroxide, ozone, sodium hypochlorite, or various permanganates may be used. Sodium hydroxide and sodium hypochlorite are commonly used (U.S. Pat. No. 4,844,874 issued Jul. 4, 1989). Hydrogen sulfide-laden process gas from the cooler-scrubber used in recycling spent reducing gas from a direct reduction iron oxide apparatus is contacted with a chlorine dioxide spray to oxidize the hydrogen sulfide to a water soluble sulfate (U.S. Pat. No. 5,447,551 issued Sep. 5, 1995 to Huestis et al.). Gases from fermentation compartments of an organic waste recycling apparatus are deodorized by serially connecting a circulatory pipe to a first deodorizing tank containing water, then to a second deodorizing tank containing a chlorine dioxide solution, preferably stabilized, and optionally to a third deodorizing tank containing activated carbon (U.S. Pat. No. 5,496,730 issued Mar. 5, 1996 to Teramachi).
The above deodorizing schemes have not been completely successful in eliminating foul odors and there is still a need for a more effective deodorizing composition, a process for its use, and an apparatus for its delivery.